Head Gasket, Intake Gasket, or Aliens?

[gglmn]

Ok, probably not aliens. My son has a 2003 Monte Carlo LS with a 3.4L, 67,000 miles. He noticed the heat wasn't working well. My first thought, check the coolant level. The reservoir tank was fine, but the radiator was low so I topped it off. Still had problems with the heat. I decided to check the water pump, thermostat, and do a flush and fill. Since I had the pump and thermostat off, I replaced each with new parts. I filled it up and did a pressure test. It held 15lbs for 10 minutes. I thought this was the fix, and took it for a test drive, no heat! Yes, I did bleed the system, though it didn’t seem to fill. I figured once the thermostat opened, the level would drop in the radiator and I would top it off after it cooled, Well here in Minnesota, it doesn’t take long to cool, so I topped it off and tried it again. Didn’t get 5 mile when the temp started to go for the 260 degree mark, and of course no heat. Well I'm guessing there's a bad gasket or warped head, or crack. Seems the leak is allowing air in the system. I’m not seeing a leak under the car nor am I seeing excessive exhaust / steam. Here’s my questions:

How can I narrow down the exact cause?

Any estimates for repairs at a shop?

Would you try to fix this yourself if this were your car?

Thanks George

[16th hippy]

you could do a number of things. start with the basics. the point of bleeding system is to get all air out. must be done with engine running, and wait for solid stream of coolant to come out. provided this is how you did that, lets move on. check oil for ANY signs of coolant. check the lower intake gaskets where the intake meets the heads(all 4 corners). is there what looks like a stream or even noticeable coolant coming out there? you could pull spark plugs to see if any are contaminated with coolant. that will help rule out head gaskets. leaking intakes can cause overheating, but so can a faulty rad cap. if system held pressure, how about the cap?

in short, start with checking cap, and check for intake leaks(very common). in any case, even if it were the head gaskets, i would repair myself. cost depends on shop and rates. let us know what you find.

[gglmn]

I forgot to mention that I did test the first cap and it was bad, only held 10lbs and was difficult to remove. I replaced it and thought that was the original cause of the coolant loss.

I'll look again for any leaks but I looked closely for any external leaks and I haven't seen any.

The oil was changed recently and I didn't see it so I'm going to take a sample from the oil pan drain to see if there's any coolant. There's no milky gunk on the oil cap cover, or dip stick.

It does seem I can't completely fill the system. I've bleed the two points I know of on the engine. One at the top of the water pump at the heater bypass, and the other on the thermostat housing. I did hook up a hose to the heater hoses and water ran freely through the heater core and engine so I don't suspect a block.

I'll be off to the library, they have AllData online available, so hopefully I can print the troubleshooting procedures. I have not pulled any codes, I'm not sure they would be of any value.

[toddler62]

I have a 2001 3.4 Monte Carlo, This engine seems to have a problem with leaking intake gaskets. Mine was replaced at 70k. I noticed the coolant level was low and the smell of burnt fluid but could'nt tell where it was leaking at. The mechanic did a pressure test and found the leak at one corner of intake gasket.

[Legacy3135]

Originally Posted by toddler62

I have a 2001 3.4 Monte Carlo, This engine seems to have a problem with leaking intake gaskets. Mine was replaced at 70k. I noticed the coolant level was low and the smell of burnt fluid but could'nt tell where it was leaking at. The mechanic did a pressure test and found the leak at one corner of intake gasket.

mine was leaking into the heads and they disassembled half the block to clean it all out.

[ChevroletTough]

Originally Posted by gglmn

.

It does seem I can't completely fill the system. I've bleed the two points I know of on the engine. One at the top of the water pump at the heater bypass, and the other on the thermostat housing. I did hook up a hose to the heater hoses and water ran freely through the heater core and engine so I don't suspect a block.

I hope when you used the hose and flushed the system, you didn't open up the valve on teh hose all the way. You need to let the water just slowly go into the block and drain out. Too much pressure will blow gaskets...

[blazes9395]

First and formost, you need to pressure test the cooling system. You need to make sure the system is holding pressure. If its holding pressure, chances are your gaskets(head & intake) are alright. If it isn't holding pressure, you need to find the problem, which could be a leaking gasket, damaged head, rad, the list goes on. If the system is holding pressure and you have no heat, disconnect the lines going to and from the heater core. Back flush it at this point. If its flowing good and is not restricted, check and make sure your rad is flowing well annd has no restrictions. If this all checks out, make sure you properly fill the cooling system and top it off. There are special procedures for these systems, so you have to make sure you follow the procedures or you'll never get all the air out properly and have problems.

[gglmn]

This is becoming a mental health issue, it’s driving me crazy!

I have pressure tested and the system holds 15# for over an hour.

Replaced the radiator cap, water pump, thermostat, all bypass hoses, and installed screw type clamps.

I flushed the system.

There are no external fluid leaks.

There is no increase in oil volume or milky color in the oil or under the cap.

Transmission fluid looks good.

No fluid leaks in the car on passenger side under heater core.

Here's the weird stuff.

Sometimes the heat works and sometime it does not. To me it almost seems as if the fluid is low and not getting to the heater core. I top off the system by filingl the radiator to the top and fill the flush connector which is in the hose from the heater core. If the heat works the temp stays at 195. If it does not, then sometimes the temp goes to about 205, and then the heat may work and the temp will fall to about 175. Sometime it will climb to about 250 and then the heat works and the temp drops to 175 to 195. Sometimes, usually when it's cold, it will climb to 260 and the warning is triggered.

I do seem to have to top off the radiator after it cools, I don't know if this is normal when purging the system of air, but it seems excessive. I thought that the fluid would be sucked back into the radiator from the reservoir I cleaned and refilled the reservoir tank. Tested the tube to the radiator for leaks, none found, and replaced the clamps with screw type clamps to prevent any fluid or air leaks.

No excessive white smoke from the exhaust or coolant smell.

When I refilled the system I followed the steps in the All Data Online:

Filling Procedure
• Tools Required
• J 23688 Coolant and Battery Fluid Tester
Notice: Refer to Fastener Notice in Service Precautions.
1. Close the radiator drain cock.
• Tighten the radiator drain cock to 2 Nm (18 inch lbs.) .
2. If the engine block drain plug was removed, perform the following:
2.1. Apply pipe sealer to the drain plug.
2.2. Install the drain plug.
• Tighten the drain plug to 22 Nm (16 ft. lbs.) .
3. Lower the vehicle.
4. Open the cooling system bleeder screws. Important: Use a 50/50 mixture of DEX-COOL antifreeze and deionized water.
5. Slowly fill the cooling system with a 50/50 coolant mixture.
6. Close the cooling system bleeder screws
7. Install the coolant pressure cap
8. Start the engine.
9. Run the engine at 2,000 - 2,500 RPM until the engine reaches normal operating temperature.
10. Allow the engine to idle for 3 minutes.
11. Shut the engine off.
12. Allow the engine to cool.
13. Top off the coolant as necessary.
14. Inspect the concentration of the engine coolant. Using the J 23688.
15. Rinse away any excess coolant from the engine and the engine compartment.
16. Inspect the cooling system for leaks.

I did not drain the block.

I'm at a loss for what to do next. Any help will surely keep me sane.

[gglmn]

I've searched the entire forum for "no heat 3.4L" and found allot of 3.4L engines have problems like mine. It seems when the engine is cold, the head or intake gaskets can leak, which allows air into the coolant system and thus causes the loss of heat. My next question is how would you proceed next? The coolant system does hold pressure but apparently a small leak in a gasket has much high pressure and puts air in the coolant. I don't want to tear the engine apart without knowing what's wrong.

[Blue Bowtie]

If the cooling system will hold 15 PSI both hot and cold, I'd suspect either compression pressure entering the cooling system or inadequate coolant flow.

[j cAT]

Originally Posted by gglmn

I've searched the entire forum for "no heat 3.4L" and found allot of 3.4L engines have problems like mine. It seems when the engine is cold, the head or intake gaskets can leak, which allows air into the coolant system and thus causes the loss of heat. My next question is how would you proceed next? The coolant system does hold pressure but apparently a small leak in a gasket has much high pressure and puts air in the coolant. I don't want to tear the engine apart without knowing what's wrong.

If you loose coolant and recover res. is full , radiator low, air in coolant system, this is usually a bad head [cracked]or head gasket.... as you know just because the oil has no coolant in it does not mean it's not head....I would check for compression in cylinders and look at plugs for evidence of this failure...also you replaced a cap that was holding 10psi to good cap 15psi and this cause more of a problem..run with no cap see if coolant starts to bubble in res...if so also bad head/gasket....did this vehicle ever have a overheat condition ? this is usually the case...

[gglmn]

Final diagnosis, blown head gasket at 67,000 miles! Caught it early so no machining was required, but I can't beleive how poorly these cars are built. What a pain in the @$$ for GM to save $1 on a gasket! I've got more miles out of my 64 MGB! No wonder no one buys American made cars!

[16th hippy]

Originally Posted by gglmn

Final diagnosis, blown head gasket at 67,000 miles! Caught it early so no machining was required, but I can't beleive how poorly these cars are built. What a pain in the @$$ for GM to save $1 on a gasket! I've got more miles out of my 64 MGB! No wonder no one buys American made cars!

glad to hear it wasn't aliens...lol. but seriously glad to hear you got it fixed, and thanks for posting solution.

[j cAT]

Originally Posted by gglmn

Final diagnosis, blown head gasket at 67,000 miles! Caught it early so no machining was required, but I can't beleive how poorly these cars are built. What a pain in the @$$ for GM to save $1 on a gasket! I've got more miles out of my 64 MGB! No wonder no one buys American made cars!

what was the condition of the coolant prior to your flushing of the system?


was the dexcool [pink] coolant clear or some other color.....?

sometimes if you do not service your vehicle yourself,,,, others my do you a favor , and add the wrong coolant to your system, this then causes problems like yours....


was the head gasket corroded ? if so beware that it could reoccur..

[momma143]

Hello I have a Chevy Monto Carlo SS 2000 Engine is 3.8.. My car was knocking and i stopped because i thought it was over heating ,Water came out all over and i left the car and had it towed to my house and didnt mess with it till next day.I put water in it and was going to turn it on and oil came out the bottom and my dad told me to check where the coolant goes and see if it is oily it was so he is thinking its a head or head gasket can you help..Im in florida and he is in Missouri so he cant help much and The junk yard we been gettin work on dont deal with this..